mongoaggregate.txt

{$expr:{$gt:[{'$subtract':['$lastUpdate','$eventStartDate']},1000*60*60*24]}}


// work
db.events.find( {$expr: {$lte:[{"$subtract":["$date","$eventStartDate"]}, 60000000]  } }   )


// เวลาผ่านไปแล้วแต่ยังไม่เคยปลัก flag ก็ต้องดึงขึ้นมาแปะป้าย

// เวลาผ่านไปแล้ว 

db.events.find( {$expr: {  $or: [ {$lte:[{"$subtract":["$date","$eventStartDate"]}, 60000000] } ,  {$eq: ["$isEventStart", false] } ]} }   )



db.events.find( $expr: {  $and: [       ]         } )




db.events.aggregate( [ { $project: { time: { $subtract: [ new Date() , "$eventStartDate" ] } }  }, {
     $addFields: {
       totalHomework: { $subtract: [ new Date() , "$eventStartDate" ] } ,
       totalQuiz: { $subtract: [ new Date() , "$eventStartDate" ] }
     }
   } ] );



db.events.aggregate( [ { $project: { totalHourSpent:{$divide : [{$subtract: ["$date","$date"]}, 3600000] }  } } ] );


db.events.aggregate([
  {
    $addFields: {
      dateDifference: {
        $subtract: [
          "$date",
          "$eventStartDate"
        ]
      }
    }
  },
])